Interesting how many different ways this device can cause problems. In my case, my 250G passport was not accessible after the first time I used it. It appeared in the Disk Manager (as active) but had no drive letter and I could not assign one to it (the error message said it was inactive).
It turned out that it somehow was associated with something called a "general volume" (generic? my system is in Swedish...) which was inactivated but appeared in the Device Manager. When I activated that, my Passport suddenly acquired a drive letter and could be accessed.
This "general volume" seems to be the same that sometimes appears when using the Safe Removal feature (and it cannot be stopped...). I have now changed the setting for the Passport so that it does not use a cache and can be removed without using Safe Removal. And so far no problems.
